The invention relates to a suspension device and a rapping mechanism for electrodes, preferably the collecting electrodes, in an electrostatic precipitator for cleaning the smoke gases from industrial plants, power supply plants and the like.
Due to the way in which such an electrostatic precipitator works, dust is deposited on its electrodes during operation and therefore they should be relieved of this dust which is effected by transmitting impact energy to the electrodes thus exposing them to intensive vibration whereby the deposited dust is released.
The impact energy required for rapping or vibrating the electrodes is usually produced by a number of hammers being lifted off their vertically suspended position by a rotating shaft which extends transversally across the precipitator width and subsequently being released so as to revert to their vertical position. For each hammer an impact rod or an impact beam is provided which is hit by the hammer when the latter reverts to its vertical position and from the impact rod/beam the supplied impact energy is then transmitted to a section of precipitator electrodes.
Rapping mechanisms of this type are known, e.g. from Duda: "Cement Data Book", 3rd edition, pp. 596-598 (Bauverlag GmbH --Wiesbaden und Berlin 1985) and patent disclosures Nos. U.S. Pat. No. 3,844,742 and GB 2,138,170.
Usually the collecting electrodes consist of vertically suspended narrow substantially rectangular plates which at their uppermost ends are fastened to a suspension arrangement in a precipitator housing. The collecting electrodes may be mounted in mutually parallel rows forming precipitator sections and rapping is preferably effected sectionwise by means of drop hammers and impact rods. The collecting electrodes may be fastened to the suspension device using e.g. bolts yielding a stiff connection. Alternatively an excentrical one-point suspension arrangement of the electrode may be employed. Such suspension arrangement is known e.g. from U.S. Pat. No. 5,051,119.
In electrostatic precipitators of the so-called European type drop hammers and impact rods are usually used which are connected to the lowermost ends of the collecting electrodes and thereby they present the disadvantage that the hammers and their supporting elements occupy comparatively much space at the end of and below the precipitator sections which, in turn, presupposes an increased length and height of the precipitator housing containing the sections.
In the so-called American-type electrostatic precipitators, the rapping of the electrodes is often effected from the top of the precipitator, the rapping mechanism then being mounted externally on top of the precipitator housing and the rapping being effected by means of vertically mounted impact rods which hit the electrode suspension arrangement vertically. In this case each impact rod is provided with slide sealings around the passage through the precipitator housing roof. Certain types of "American" precipitators may alternatively be provided with a vertically acting rapping mechanism mounted inside the precipitator housing which actuates the electrodes axially. Moreover, when American-type precipitators are used having the rapping mechanism mounted on top of the precipitator housing roof, the volume occupied by the aggregate precipitator in the relevant plant is substantially increased.